Tubeless tires have largely replaced tires with inner tubes for virtually all sizes of tires, ranging from passenger car tires to large tires used on off-road vehicles such as tractors and graders. It is necessary to maintain an air-tight tire casing, which means that any punctures which occur must be repaired or else the tire must be replaced. It is particularly important to repair rather than replace large tires for off-road vehicles where possible, because of the cost of such tires and the frequency with which punctures occur, due to severe conditions of use.
Patch compounds and techniques for tire repair are well known. For example, it is known that a tire having a puncture can be repaired by applying a patch compound to the puncture side, applying pressure by means of air bags on both the inside and outside of the tire at the repair side, and applying heat sufficient to vulcanize the patched material. Various patch compounds are known; a representative compound comprises rubber reinforced with nylon fibers. A problem occurs with respect to application of pressure to the inside of the tire because of the large space from the inside of the tire to the bead set. Heretofore, various methods have been used to fill the gap such as various mandrels or space filling material which is cumbersome and time consuming to insert and remove, difficult to adjust in size and generally hard to utilize. A further difficulty with presently known techniques is that they do not apply uniform pressure which can be sustained for at least sufficient time to permit the patch compound to cure.